<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    // 需要一个临时变量帮助我们
    var a = 10;
    var b = 20;
    var c;
    c = a;
    a = b;
    b = c;
    console.log("a:",a)
    console.log("b:",b)
</script>
</body>
</html>